QApplication in Shared Library

Question

I have minimal example of a program. It functions when compiled as an app, but fails as a shared library. Why is this?

interface.h

#include <QObject>
#include <QApplication>
#include <QPushButton>
#include <QThread>

#ifdef __cplusplus
#define EXTERNC extern "C"
#else
#define EXTERNC
#endif

EXTERNC void initialize();

#undef EXTERNC

class Q_DECL_EXPORT SharedLibrary :public QObject {
    Q_OBJECT

public:
    SharedLibrary();

private:
    QCoreApplication * app;
};

interface.cpp

#include "interface.h"
#define UNUSED(x) (void)(x)

SharedLibrary::SharedLibrary() {
    int argc = 1;
    char* argv[] = { (char*)"sharedlibrary.lib", NULL };

    app = new QApplication(argc, argv);
    QPushButton button("Hello World");
    button.show();
    app->exec();
}

void initialize() {
    new SharedLibrary();
    return;
}

int main (int argc, char** argv) {
    UNUSED(argc);
    UNUSED(argv);
    new SharedLibrary();
    return 0;
}

When I compile my application as an app and run main it works just fine. When I compile my application as a lib and run initialize it crashes. Interestingly enough, the same exact code works on Linux. Full stack trace below:

arithmetic error FLOATING-POINT-INVALID-OPERATION signalled
   [Condition of type FLOATING-POINT-INVALID-OPERATION]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [*ABORT] Return to SLIME's top level.
 2: [ABORT] abort thread (#<THREAD "repl-thread" RUNNING {1002E605A3}>)

Backtrace:
  0: ("bogus stack frame")
  1: ("foreign function: CUIDraw")
  2: ("foreign function: _HIThemeCUIDrawWithOptions")
  3: ("foreign function: _HIThemeCUIDrawWithRenderer")
  4: ("foreign function: _HIThemeDrawAppleMenuTitle")
  5: ("foreign function: _ZN13HIMenuBarView8DrawOnceE6CGRectS0_bbP9CGContext")
  6: ("foreign function: _ZN13HIMenuBarView8DrawSelfEsPK9__HIShapeP9CGContext")
  7: ("foreign function: _ZN6HIView12EventHandlerEP25OpaqueEventHandlerCallRefP14OpaqueEventRefPv")
  8: ("foreign function: _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec")
  9: ("foreign function: _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec")
 10: ("foreign function: SendEventToEventTargetWithOptions")
 11: ("foreign function: _ZN6HIView8SendDrawEsP13OpaqueGrafPtrPK9__HIShapeP9CGContext")
 12: ("foreign function: _ZN6HIView23RecursiveDrawCompositedEPK9__HIShapeS2_jPS_P9CGContexthd")
 13: ("foreign function: _ZN6HIView23RecursiveDrawCompositedEPK9__HIShapeS2_jPS_P9CGContexthd")
 14: ("foreign function: _ZN6HIView14DrawCompositedEsP13OpaqueGrafPtrPK9__HIShapejPS_P9CGContext")
 15: ("foreign function: _ZN6HIView6RenderEjP9CGContext")
 16: ("foreign function: _ZN10WindowData20PrepareForVisibilityEv")
 17: ("foreign function: _ShowHideWindows")
 18: ("foreign function: ShowHide")
 19: ("foreign function: _ZN9MBWindows18GetWindowOnDisplayEjh")
 20: ("foreign function: _ZN15MenuBarInstance15ForEachWindowDoEhU13block_pointerFbP15OpaqueWindowPtrjE")
 21: ("foreign function: _ZN15MenuBarInstance4HideE21MenuBarAnimationStylehhPhh")
 22: ("foreign function: _ZN15MenuBarInstance21UpdateAggregateUIModeE21MenuBarAnimationStylehhh")
 23: ("foreign function: _ZN15MenuBarInstance16ForEachMenuBarDoEU13block_pointerFvPS_E")
 24: ("foreign function: _ZL25UpdateAllAggregateUIModes21MenuBarAnimationStyleh")
 25: ("foreign function: SetSystemUIMode")
 26: ("foreign function: -[NSApplication _setPresentationOptions:instance:flags:]")
 27: ("foreign function: qt_plugin_instance")
 28: ("foreign function: #x8B2BAB2")
 29: ("foreign function: _ZN27QPlatformIntegrationFactory6createERK7QStringRK11QStringListRiPPcS2_")
 30: ("foreign function: _ZN27QPlatformIntegrationFactory6createERK7QStringRK11QStringListRiPPcS2_")
 31: ("foreign function: _ZN22QGuiApplicationPrivate25createPlatformIntegrationEv")
 32: ("foreign function: _ZN22QGuiApplicationPrivate21createEventDispatcherEv")
 33: ("foreign function: _ZN23QCoreApplicationPrivate4initEv")
 34: ("foreign function: _ZN22QGuiApplicationPrivate4initEv")
 35: ("foreign function: _ZN19QApplicationPrivate4initEv")
 36: ("foreign function: _ZN13SharedLibraryC2Ev")
 37: ("foreign function: initialize")
 38: (CL-WEBENGINE::INITIALIZE)
 39: (SB-INT:SIMPLE-EVAL-IN-LEXENV (CL-WEBENGINE::INITIALIZE) #<NULL-LEXENV>)
 40: (EVAL (CL-WEBENGINE::INITIALIZE))
 41: (SWANK::EVAL-REGION "(cl-webengine::initialize) ..)
 42: ((LAMBDA NIL :IN SWANK-REPL::REPL-EVAL))
 43: (SWANK-REPL::TRACK-PACKAGE #<CLOSURE (LAMBDA NIL :IN SWANK-REPL::REPL-EVAL) {100318C0AB}>)
 44: ((LAMBDA NIL :IN SWANK-REPL::REPL-EVAL))
 45: (SWANK::CALL-WITH-RETRY-RESTART "Retry SLIME REPL evaluation request." #<CLOSURE (LAMBDA NIL :IN SWANK-REPL::REPL-EVAL) {100318C04B}>)
 46: ((LAMBDA NIL :IN SWANK-REPL::REPL-EVAL))
 47: (SWANK/BACKEND:CALL-WITH-SYNTAX-HOOKS #<CLOSURE (LAMBDA NIL :IN SWANK-REPL::REPL-EVAL) {100318C02B}>)
 48: (SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<CLOSURE (LAMBDA NIL :IN SWANK-REPL::REPL-EVAL) {100318C02B}>)
 49: (SWANK-REPL::REPL-EVAL "(cl-webengine::initialize) ..)
 50: (SWANK-REPL:LISTENER-EVAL "(cl-webengine::initialize) ..)
 51: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SWANK-REPL:LISTENER-EVAL "(cl-webengine::initialize) ..)
 52: (EVAL (SWANK-REPL:LISTENER-EVAL "(cl-webengine::initialize) ..)
 53: (SWANK:EVAL-FOR-EMACS (SWANK-REPL:LISTENER-EVAL "(cl-webengine::initialize) ..)
 54: (SWANK::PROCESS-REQUESTS NIL)
 55: ((LAMBDA NIL :IN SWANK::HANDLE-REQUESTS))
 56: ((LAMBDA NIL :IN SWANK::HANDLE-REQUESTS))
 57: (SWANK/SBCL::CALL-WITH-BREAK-HOOK #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA NIL :IN SWANK::HANDLE-REQUESTS) {1002E680FB}>)
 58: ((FLET SWANK/BACKEND:CALL-WITH-DEBUGGER-HOOK :IN "/Users/jmercouris/.emacs.d/elpa/slime-20200228.1656/swank/sbcl.lisp") #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA NIL :IN SWANK::HANDLE-RE..
 59: (SWANK/BACKEND:CALL-WITH-DEBUGGER-HOOK #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA NIL :IN SWANK::HANDLE-REQUESTS) {1002E680FB}>)
 60: ((LAMBDA NIL :IN SWANK::HANDLE-REQUESTS))
 61: (SWANK::CALL-WITH-BINDINGS ((*STANDARD-INPUT* . #<SWANK/GRAY::SLIME-INPUT-STREAM {1002E2F8E3}>)) #<CLOSURE (LAMBDA NIL :IN SWANK::HANDLE-REQUESTS) {1002E6811B}>)
 62: ((FLET "FORM-FUN-5" :IN SWANK::HANDLE-REQUESTS))
 63: (SWANK::HANDLE-REQUESTS #<SWANK::MULTITHREADED-CONNECTION {1002C0B143}> NIL)
 64: (SWANK-REPL::REPL-LOOP #<SWANK::MULTITHREADED-CONNECTION {1002C0B143}>)
 65: ((LAMBDA NIL :IN SWANK-REPL::SPAWN-REPL-THREAD))
 66: (SWANK::CALL-WITH-BINDINGS NIL #<CLOSURE (LAMBDA NIL :IN SWANK-REPL::SPAWN-REPL-THREAD) {1002E680DB}>)
 67: ((LAMBDA NIL :IN SWANK-REPL::SPAWN-REPL-THREAD))
 68: ((FLET SB-UNIX::BODY :IN SB-THREAD::NEW-LISP-THREAD-TRAMPOLINE))
 69: ((FLET "WITHOUT-INTERRUPTS-BODY-4" :IN SB-THREAD::NEW-LISP-THREAD-TRAMPOLINE))
 70: ((FLET SB-THREAD::WITH-MUTEX-THUNK :IN SB-THREAD::NEW-LISP-THREAD-TRAMPOLINE))
 71: ((FLET "WITHOUT-INTERRUPTS-BODY-1" :IN SB-THREAD::CALL-WITH-MUTEX))
 72: (SB-THREAD::CALL-WITH-MUTEX #<CLOSURE (FLET SB-THREAD::WITH-MUTEX-THUNK :IN SB-THREAD::NEW-LISP-THREAD-TRAMPOLINE) {7A4DE7B}> #<SB-THREAD:MUTEX "thread result lock" owner: #<SB-THREAD:THREAD "repl-thr..
 73: (SB-THREAD::NEW-LISP-THREAD-TRAMPOLINE #<SB-THREAD:THREAD "repl-thread" RUNNING {1002E605A3}> NIL #<CLOSURE (LAMBDA NIL :IN SWANK-REPL::SPAWN-REPL-THREAD) {1002E6054B}> NIL)
 74: ("foreign function: call_into_lisp")
 75: ("foreign function: new_thread_trampoline")

here is what my .pro file looks like:

TEMPLATE = lib
TARGET = webengine
INCLUDEPATH += .
QT += core gui widgets webenginewidgets

# Input
HEADERS += interface.h
SOURCES += interface.cpp

Answer 1

I've figured out the answer, at least for my application, apparently I have to change the behavior of the code that interacts with my shared library:

(sb-int:with-float-traps-masked (:invalid :inexact :overflow) (cl-webengine::run))

in order to have a successful execution.